/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.io.synthetic;



import com.bff.gaia.unified.sdk.io.range.OffsetRange;



import java.io.Serializable;

import java.util.ArrayList;

import java.util.List;





import static org.apache.commons.math3.stat.StatUtils.sum;



/** Determines bundle sizes based on @{link SyntheticSourceOptions}. */

public class BundleSplitter implements Serializable {



  private SyntheticSourceOptions options;



  public BundleSplitter(SyntheticSourceOptions options) {

    this.options = options;

  }



  List<OffsetRange> getBundleSizes(int desiredNumBundles, long start, long end) {

    List<OffsetRange> result = new ArrayList<>();



    double[] relativeSizes = getRelativeBundleSizes(desiredNumBundles);



    // Generate offset ranges proportional to the relative sizes.

    double s = sum(relativeSizes);

    long startOffset = start;

    double sizeSoFar = 0;

    for (int i = 0; i < relativeSizes.length; ++i) {

      sizeSoFar += relativeSizes[i];



      long endOffset =

          (i == relativeSizes.length - 1) ? end : (long) (start + sizeSoFar * (end - start) / s);



      if (startOffset != endOffset) {

        result.add(new OffsetRange(startOffset, endOffset));

      }

      startOffset = endOffset;

    }

    return result;

  }



  private double[] getRelativeBundleSizes(int desiredNumBundles) {

    double[] relativeSizes = new double[desiredNumBundles];

    for (int i = 0; i < relativeSizes.length; ++i) {

      relativeSizes[i] =

          options.bundleSizeDistribution.sample(options.hashFunction().hashInt(i).asLong());

    }

    return relativeSizes;

  }

}